Push-back racks are known in the art. These racks are very efficient means for storing goods on pallets, because the pallets can be loaded and unloaded from the front of the rack and can be stored two or more deep in the rack, thereby conserving floor space.
These racks have a large number of storage chambers, each having support rails which lead from the back of the rack to a front opening into which the pallets full of goods are loaded and from which they are unloaded. The support rails are inclined slightly downward toward the front of the rack and carry one or more carts having wheels which ride on the support rails. The carts nest with each other, and, when the carts are empty, they all roll by gravity to the front of the rack to be loaded. The first cart is the highest and receives the first load. When a forklift truck comes with the second load, it pushes the first cart back to uncover a second cart, which receives a second load, and so forth, until all the carts are used up, and the last load is placed directly on the support rails.
In the past, each cart has had its own set of rails on which to ride, so, as more carts are added, additional rails had to be added, making the racks much more expensive. Also, as each new cart was added, the rails had to become wider apart, and the carts had to become wider in order to ride o the rails and straddle the other carts. This widening of each storage chamber to accommodate the additional carts began to defeat the purpose of using push-back racks to conserve storage space. Some manufacturers have created elaborate carts which ride on each other to try to alleviate this problem, but then the carts become expensive.
Also, in the prior art, every set of rails had to extend all the way to the front opening of the storage chamber, because every cart rode on its own set of rails and had to roll to the front of the storage chamber for loading and unloading. The amount of material required for all these rails was substantial and had a large impact on the cost of the rack.